Summit Vision Center

KUTV news on Sunglasses and UV protection

Dr. Langford April 10th, 2006

I just watched a blip on KUTV news where they bought several pairs of sunglasses and tested them all to check how well they filtered out UV light. They said you can get a cheap pair of sunglasses that says “400 UV” which does the same job as the expensive ones.

Let me clarify a few things. The sunwear should say something like “UV400″ to let you know that it claims to filter out both UV-A and UV-B wavelengths.

A factor the newscast did not consider is one of ophthalmic lens quality. At optometry school, a professor of mine, Dr. Karl Citek, had heard about some people getting eyestrain while driving with sunglasses. He postulated that perhaps the non-prescription sunwear lenses induced prism. Using mild prism on someone who doesn’t need it causes the eyes to want to turn in or out to avoid seeing double. He measured in a lensometer the prism of the lens. Surprisingly, there was no prism measured! Back to the drawing board, he realized another way of detecting prism in glasses besides a lensometer is to shine a laser light through the lens. If the light beam redirected its path after travelling through the cheap sunglass lens, then it had a prism effect even though the lensometer method didn’t detect it.

He devised a rig to test various sunglasses by his laser method, and found many lenses bent the light. Some cheap sunglasses were fine, others actually induced prism.

So, how is a consumer supposed to know which cheap sunglasses are okay? You can’t. We need Dr. Citek’s patent-pending laser jig thingy. I do know that Dr. Citek holds patents and works a lot with Nike ophthalmic lenses, so you are very safe buying Nike sunwear. In fact, his patent that Nike sunwear uses not only stops induced/unnessary prism, it also keeps your eyes from experiencing unwanted astigmatism at the edge of the lens.

Dr. Citek also has done azeresearch regarding the issue of UV light and whether cleaning them affects UV blocking (it doesn’t). (Poster #121 page 62 in the pdf file.)

If you do have a concern about how much UV light is passing through your sunglasses, we do have a UV testor at Summit Vision Center, so stop by and check it out. Our frame and lens specialist can also direct you to our great line of quality sunwear. I personally recommend always using polarized sunwear to decrease glare while driving, golfing, and during water and snow sports.

(If any golfers want to take issue with me regarding polarized glasses, then please see Dr. Citek’s research regarding this subject (poster #70, page 36 in the pdf). It finds that polarized lenses DO NOT detract from putting performance.)